稍微做了一点儿修改

/**

     * 利用NetworkImageView显示网络图片

     */

    private void showImageByNetworkImageView(){

        String imageUrl="http://avatar.csdn.net/6/6/D/1_lfdfhl.jpg";

        RequestQueue requestQueue = Volley.newRequestQueueInDisk(ctx, "/sdcard/demo/", null);

        ImageLoader imageLoader = new ImageLoader(requestQueue, new BitmapCache());  

        mNetworkImageView.setTag("url");

        mNetworkImageView.setImageUrl(imageUrl,imageLoader);

    }  

import org.json.JSONObject;

import android.app.Activity;

import android.app.ProgressDialog;

import android.content.Context;

import android.os.Bundle;

import android.widget.ImageView;

import com.android.volley.Request;

import com.android.volley.RequestQueue;

import com.android.volley.Response;

import com.android.volley.VolleyError;

import com.android.volley.toolbox.ImageLoader;

import com.android.volley.toolbox.ImageLoader.ImageListener;

import com.android.volley.toolbox.JsonObjectRequest;

import com.android.volley.toolbox.NetworkImageView;

import com.android.volley.toolbox.Volley;

public class MainActivity extends Activity {

    private Context ctx;

    private RequestQueue mQueue;

    private ImageLoader mImageLoader;

    private ImageView mImageView;

    private NetworkImageView mNetworkImageView;  

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        this.ctx = this;

        initView();

        showImageByNetworkImageView();

    }

    private void initView(){

        mImageView=(ImageView) findViewById(R.id.imageView);

        mNetworkImageView=(NetworkImageView)findViewById(R.id.networkImageView);

    }

    /**

     * 利用Volley获取JSON数据

     */

    private void getJSONByVolley() {

        RequestQueue requestQueue = Volley.newRequestQueue(this);

        String JSONDataUrl = "http://pipes.yahooapis.com/pipes/pipe.run?_id=giWz8Vc33BG6rQEQo_NLYQ&_render=json";

        final ProgressDialog progressDialog = ProgressDialog.show(this, "This is title", "...Loading...");  

        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(

                Request.Method.GET,

                JSONDataUrl,

                null,

                new Response.Listener<JSONObject>() {

                    @Override

                    public void onResponse(JSONObject response) {

                        System.out.println("response="+response);

                        if (progressDialog.isShowing()&&progressDialog!=null) {

                            progressDialog.dismiss();

                        }

                    }

                },

                new Response.ErrorListener() {

                    @Override

                    public void onErrorResponse(VolleyError arg0) {

                           System.out.println("sorry,Error");

                    }

                });

        requestQueue.add(jsonObjectRequest);

    }  

    private void loadImageByVolley(){

        String imageUrl="http://avatar.csdn.net/6/6/D/1_lfdfhl.jpg";

        RequestQueue requestQueue = Volley.newRequestQueue(this);  

        ImageLoader imageLoader = new ImageLoader(requestQueue, new BitmapCache());

        ImageListener listener = ImageLoader.getImageListener(mImageView, R.drawable.ic_launcher,R.drawable.ic_launcher);

        imageLoader.get(imageUrl, listener);

    }  

    /**

     * 利用NetworkImageView显示网络图片

     */

    private void showImageByNetworkImageView(){

        String imageUrl="http://avatar.csdn.net/6/6/D/1_lfdfhl.jpg";

        RequestQueue requestQueue = Volley.newRequestQueueInDisk(ctx, "/sdcard/demo/", null);

        ImageLoader imageLoader = new ImageLoader(requestQueue, new BitmapCache());  

        mNetworkImageView.setTag("url");

        mNetworkImageView.setImageUrl(imageUrl,imageLoader);

    }  

}

import android.graphics.Bitmap;

import android.support.v4.util.LruCache;

import com.android.volley.toolbox.ImageLoader.ImageCache;

public class BitmapCache implements ImageCache {

    private LruCache<String, Bitmap> mCache;  

    public BitmapCache() {

        int maxSize =  *  * ;

        mCache = new LruCache<String, Bitmap>(maxSize) {

            @Override

            protected int sizeOf(String key, Bitmap value) {

                return value.getRowBytes() * value.getHeight();

            }

        };

    }  

    @Override

    public Bitmap getBitmap(String url) {

        return mCache.get(url);

    }  

    @Override

    public void putBitmap(String url, Bitmap bitmap) {

        mCache.put(url, bitmap);

    }

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

     >  

    <com.android.volley.toolbox.NetworkImageView

        android:id="@+id/networkImageView"

        android:layout_width="120dip"

        android:layout_height="120dip"

        android:layout_centerHorizontal="true"

        android:layout_marginTop="30dip"

    />  

     <ImageView

        android:id="@+id/imageView"

        android:layout_width="120dip"

        android:layout_height="120dip"

        android:layout_centerInParent="true"

    />  

</RelativeLayout>